small copper wire in '73 bosch distributor

[tmctguer]

while doing my rotor, cap, and points change on my '73 bosch distributor, i noticed a very small braided copper wire going from the plate used to mount the points and going to the side of the distributor housing.

this wire seems to be a 'ground' of some kind. it seems to be hard soldered on each end to its respective connection point.

on my distribributor, the wire seems to be quite frayed, and the end soldered to the "points mounting plate" seems to be breaking away from the plate.

does anyone know what this wire is for, and what affect it would have on the car if that wire broke?

(this has early S man written all over it)

[Matt Smith]

Or his faithful student.

It is a ground for the points plate. Remember this thing moves when the vacuum advance (for us, retard) operates, so there needs to be a flexible wire there to pass the current. I guess they didn't think the pivot itself was reliable enough at passing current, so it's like a back up strap?
If it broke you would probably loose power. The points in a cdi system are used only as a trigger and don't pass much current. I think Mr Hall himself suffered a failure of this nature some time ago.

[tmctguer]

mine is near breaking. i'm wondering if i need to attempt to re-solder each end?

[jkeyzer]

If this wire breaks you may or may not lose your spark. It depends on how good of a connection to ground you get from the moving vacuum advance plate down to the plate underneath it which is affixed to the body of the distributor. I would guess it could be very flakey.

It looks like originally the ground strap was cold welded. I'm not sure what the plate is made of but you may have trouble getting solder to stick.

And yeah I am sure Early S Man will have the scoop.

[Early_S_Man]

TMC et al,

Yes, it broke at 49K miles on my car, in 1982, and killed the engine DEAD because of no spark ... about 1/2 mile from the house.

The pics below show the break and the completed repair job. The original strap is spot/resistance welded to the nickel-plated point plate and anchor mount.

Soldering won't work, but a very easy repair is to make a new strap of braid or stranded wire, and solder small eyelet/lugs on each end that can be secured under available screws ... one of the point's anchor screws at the 'flex' end and one of the body screws atthe fixed end. Permanent end of problem!

About three years after I did my repair, I bought a 184-series RS 2.7 distributor from PMO, and found out Bosch fixed the problem in later production variant by switching to a braided strap and crimping a lug onto the ends of the strap and spot/resistance welding both braid and terminal lug to the nickel-plated steel point plate and mounting base plate.

Notice on the pics below that I put heat shrink on the strap where it goes by the points' Faston connector. In the upper pic, the point of the break occurred at the end of the strap immediately at the point where the spot weld terminated at the strap at the 'flexing' end of the strap. That stress point is eliminated in my repair and in the later Bosch crimped straps ... because the entire braided strap is forced to flex, instead of the stranded wires at the point of the spot weld!

[tobluforu]

So, how many non-guru's(like myself) had this happen to them and spent days trying to figure it out or, had it towed to the shop?

[Roland Kunz]

Hello


The groundwire is easy to trail even worser is if the sliding points burned away ( as the ground wire was missing ? ).

Grüsse

[tmctguer]

uhhhhh...............what ??

[Roland Kunz]

Hello

The plate slides on small lead dots and if they are gone it makes a - stick slip - motion or only makes half the motion.

You can´t see it you can´t, messure it direct and it starts only making problems at random shooting so you hunt a unreproducable thing.

This leads to replacing the distributor with a rebuild ( secure ) unit to troubleshoot problems on the ignition.

Many people go the wrong way and start with the main things and replace the CDI unit or other components before they start troubleshooting the absolute basic things.
Well thats why I never become rich, I sale a rebuilt distributor while others sale complete ignition systems to fix the same problem.

Grüsse